"This is what we do, and we treat everything very serious, so when this came down we just went into what our protocol is. We practice this type of thing,” said Lt. Richard Lally.

Authorities said they did not need to evacuate the building during the investigation.

“Generally, in cases like this, you don't do that because if there is some agent that is dangerous you want to keep the people where you can see them and find them if you need to get them medically treated,” said Paul Cohen, Public Building Commission administrator.

Investigators were quick to determine the substance was harmless, but they are still determining how the powder got there. They said it did not come in the mail.

“We're pretty much sure that it wasn't an accidental spill by the people in that office. Beyond that, it's anyone's guess why it was done or how it got there,” Cohen said.

Lally said the test of the powder came back as a food additive or protein.

The Sheriff’s Office will handle the investigation internally and turn the case over to the criminal investigation division.

The Planning Department and Housing and Urban Development have offices on the 11th floor.

Copyright 2013 byKETV.com All rights reserved. This material may not be published, broadcast, rewritten or redistributed.